1. Field of the Invention
The present invention relates to an engine starting device for starting an internal combustion engine using an electric motor connected to the output shaft of the engine.
2. Background Information
Japanese Laid-Open Patent Publication No. 2001-263209 discloses a conventional engine starting device that stops the engine while idling to improve fuel economy. The conventional engine starting device starts an motor when a command is received to generate a predetermined starting torque in the motor when restarting the engine, and performs feedback control of the power supplied to the motor so that the actual motor rotation speed matches a target rotation speed when the motor rotation speed reaches a predetermined rotation speed near the target rotation speed.
There are engines, which are installed in idling stop vehicles, in which an intake valve closed position or timing is retarded toward the compression top dead center when the engine is restarted in order to improve fuel consumption and to reduce vibration. With such engines, since there is low charging efficiency per unit cylinder in this type of engines (i.e., the amount of air to be compressed in the cylinder is small), the compression temperature of the piston is low. Therefore, it is difficult for the engine to start combustion (e.g., it is difficult to ignite the air-fuel mixture) unless the compression process is repeated several times, particularly when the vehicle is operating in a low temperature environment.